Strain Measurement System

Abstract

To provide a strain measurement system capable of starting strain measurement immediately after erecting a steel shoring and predicting natural ground behavior in real time.SOLUTION: A strain measurement system that measures the strain of steel shoring installed in tunnels, including: a strain measuring device 10 that is attached to a steel shoring and wirelessly transmits measurement data including a strain measurement value being measured; and a monitoring device 20 that is installed in a drill jumbo, that is a work vehicle for tunnel construction working in front of a pit face, and monitors the strain of the steel shoring based on the measurement data received from the strain measuring device 10. The monitoring device 20 comprises a strain monitoring unit 43 in which the measurement data at the time of reception is compared with the past measurement data, and a warning is issued when the amount of change in the strain measurement value exceeds a preset danger threshold.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a strain measurement system that measures strain in steel supports installed in a tunnel. [Background technology]

[0002] In mountain tunnel construction, when the soil covering is thin and the ground strength ratio is low, or when the ground is expansive, there is a possibility that large earth pressure will be generated on the steel supports. Therefore, strain measurements (stress measurements) of the steel supports may be carried out to confirm their stability and appropriateness (dimensions, pitch, etc.).

[0003] For example, technology is being considered for measuring the internal displacement of structures such as tunnels and monitoring deformation of the structures (see, for example, Patent Document 1). In the technology disclosed in this document, one end of a beam that serves as an internal displacement sensor is fixed inside the structure, and a device capable of measuring strain is installed on the surface of the beam, and the vertical and horizontal displacements of the structure are calculated from the measured strain. Then, a strain measuring device acquires a signal from a strain detection device attached to the internal displacement sensor.

[0004] Also, a measurement system for grasping the behavior of a tunnel lining during an earthquake in real time is being considered (for example, see Patent Document 2). In the tunnel lining behavior measurement system disclosed in this document, a sensor having a strain gauge and a wireless transmission device connected to the sensor are placed on the tunnel lining surface. Information on the deformation of the tunnel lining surface from the wireless transmission device is received by a wireless receiving device outside the tunnel, and the deformation information of the lining surface is analyzed by a tunnel lining deformation information analysis device. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2013-047629 A [Patent Document 2] JP 2009-300323 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the conventional technology, when measuring strain on steel supports, the strain gauges installed on the steel supports are connected to a data logger by wire. Therefore, in order to start strain measurement, it is necessary to temporarily stop excavation and run cables to the rear where the excavation does not affect, so strain measurement cannot be started immediately after erecting the steel supports. In addition, the cables are laid on the side walls, so they also need to be protected, which is time-consuming and costly.

[0007] In addition, the measured strain data is collected in a data logger at the end of the cable. Therefore, if a large amount of strain occurs, there is a risk that the emergency evacuation command to the tunnel face may be delayed due to the distance between the data logger and the tunnel face.

[0008] Furthermore, the conventional technology did not measure the distance between the strain measurement point and the excavation face where excavation progresses day by day, which meant it was not possible to predict ground behavior in real time.

[0009] The present invention has been made in consideration of the above-mentioned situation, and aims to provide a strain measurement system that resolves the above-mentioned problems, can start measuring strain immediately after the steel support structure is erected, and can predict ground behavior in real time. [Means for solving the problem]

[0010] The strain measurement system of the present invention is a strain measurement system that measures strain in a steel support installed in a tunnel, and includes a strain measurement device that is attached to the steel support and wirelessly transmits measurement data including a measured strain measurement value, and a monitoring device that is installed in a tunnel construction vehicle working in front of the tunnel face and monitors the strain in the steel support using the measurement data received from the strain measurement device. The monitoring device includes a measurement distance estimation unit that estimates a measurement distance to a face at the time of measurement based on radio wave intensity at the time of receiving the measurement data, an unknown quantity estimation unit that estimates a natural ground elastic modulus and an initial stress as natural ground characteristics by an inverse analysis method using the strain measurement value and the measurement distance as measurement numbers, and a suitability determination unit that calculates internal displacement and shear stress distribution by a forward analysis using the natural ground characteristics and compares them with management values ​​to confirm the suitability of the support.The present invention is characterized by the above. Furthermore, in the strain measurement system of the present invention, the monitoring device includes a strain monitoring unit that, upon receiving the measurement data, compares the received measurement data with past measurement data, and issues a warning if the amount of change in the strain measurement value exceeds a preset danger threshold. 。 difference Furthermore, in the strain measurement system of the present invention, the measurement distance estimation unit calculates the measurement distance based on the straight-line distance between the strain measurement device and the monitoring device estimated based on the radio wave intensity at the time the measurement data is received, the straight-line distance between the tunnel face on which the steel support to which the strain measurement device is attached is installed and the monitoring device, and the distance between the face and the monitoring device. Effect of the Invention

[0011] According to the present invention, since no cable wiring or protective work is required to install a strain measuring device, excavation does not need to be stopped in order to install the strain measuring device, and strain measurement and monitoring can be started near the face immediately after the steel support 1 is erected, resulting in the effect of being able to predict ground behavior in real time. [Brief description of the drawings]

[0012] [Figure 1] 1 is a system configuration diagram showing a configuration of an embodiment of a strain measurement system according to the present invention. [Diagram 2] FIG. 2 is a block diagram showing the configuration of the strain measurement system shown in FIG. [Diagram 3] 3 is a diagram illustrating an analytical model of an unknown quantity estimation operation performed by an unknown quantity estimation unit illustrated in FIG. 2. [Figure 4] 3 is an explanatory diagram for explaining a measured distance estimation operation by a measured distance estimation unit shown in FIG. 2; [Diagram 5] 3 is a flowchart showing an unknown quantity estimating operation and a compatibility determining operation by an unknown quantity estimating unit and a compatibility determining unit shown in FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Next, a mode for carrying out the present invention (hereinafter simply referred to as an "embodiment") will be specifically described with reference to the drawings. Referring to FIG. 1, the strain measurement system of this embodiment includes a strain measurement device 10 attached to a steel support 1 and a monitoring device 20 installed in a drill jumbo 2 .

[0014] The steel support 1 is an arch-shaped steel material used in the New Austrian Tunneling Method (NATM) for constructing tunnels. In the NATM method, the steel support 1 is erected on the tunnel wall near the tunnel face every time a tunnel is excavated, and the steel support 1 is installed at preset intervals L.

[0015] The strain measuring devices 10 are attached to the steel supports 1 before they are erected, and are installed inside the tunnel when the steel supports 1 are erected. In this embodiment, the strain measuring devices 10 are attached to three locations on the ceiling surface and both side surfaces of the steel supports 1, but there are no particular limitations on the locations and number of the strain measuring devices 10 to be attached.

[0016] The drill jumbo 2 is a tunnel construction vehicle that performs work in front of the tunnel face. The monitoring device 20 may be installed on another tunnel construction vehicle, such as an erector, instead of the drill jumbo 2.

[0017] Referring to FIG. 2, the strain measuring device 10 includes a strain gauge 11, a bridge 12, an amplifier 13, a strain measuring section 14, a measurement result storage section 15, a communication control unit 16, a wireless unit 17, and a battery 18.

[0018] The strain gauge 11 is attached to the surface of the steel support 1, and is a sensor whose physical property value (resistance value in this embodiment) changes according to the stress (strain) applied to the steel support 1. In this embodiment, two strain gauges 11 are provided, but the number of strain gauges 11 is not particularly limited.

[0019] The bridge 12 is a circuit (e.g., a Wheatstone bridge) that uses the strain gauge 11 as a resistor to measure a resistance value corresponding to a change in strain and outputs the resistance value as a strain measurement signal. The strain measurement signal output from the bridge 12 is amplified by an amplifier 13 and input to a strain measurement unit 14.

[0020] The strain measuring unit 14 is an information processing unit that operates under program control. The strain measuring unit 14 measures, as a strain measurement value, the signal intensity of the strain measurement signal input from the bridge 12 via the amplifier 13. In this embodiment, the strain measuring unit 14 measures the strain measurement value at one-minute intervals for 24 hours after the start of the strain measuring device 10, and at ten-minute intervals after 24 hours.

[0021] The communication control unit 16 is a control unit that controls wireless communication with the monitoring device 20, and converts the measurement data output from the strain measuring unit 14 into a wireless signal. Then, the wireless unit 17 transmits a wireless signal of a preset strength via an antenna. In this embodiment, a communication distance of about 20 m is ensured by using a frequency in the 920 MHz band.

[0022] The strain measurement unit 14 determines whether the communication control unit 16 is in a state where wireless communication with the monitoring device 20 is possible, and if wireless communication with the monitoring device 20 is possible, transmits measurement data consisting of the measured strain measurement value and a unique device ID to the monitoring device 20 via the communication control unit 16 and the wireless unit 17.

[0023] When wireless communication with the monitoring device 20 is not possible, the strain measuring unit 14 stores the measured strain measurement value together with timing data indicating the measurement timing (time, measurement order, interval, etc.) in the measurement result storage unit 15 constituted by a flash memory or the like. Then, when wireless communication with the monitoring device 20 becomes possible, the strain measuring unit 14 transmits to the monitoring device 20 measurement data consisting of the strain measurement value and timing data stored in the measurement result storage unit 15, and a unique device ID.

[0024] The battery 18 is a power supply unit that supplies power to each unit of the strain measuring device 10, and in this embodiment has a capacity that can ensure the measurement and transmission operations of the strain measuring device 10 continue for one month or more.

[0025] The monitoring device 20 includes a wireless unit 21, a communication control unit 22, and an analysis device 30. The wireless signal transmitted from the strain measuring device 10 is received by the wireless unit 21 of the monitoring device 20 via an antenna, and the communication control unit 22 demodulates the wireless signal received by the wireless unit 21 into measurement data. Then, the communication control unit 22 outputs the demodulated measurement data to the analysis device 30 together with the reception strength when the wireless unit 21 received the wireless signal from the strain measuring device 10.

[0026] The monitoring device 20 is installed on the drill jumbo 2 that travels inside the mine. Therefore, when the drill jumbo 2 travels inside the mine, the monitoring device 20 can comprehensively receive measurement data from the strain measuring devices 10 installed inside the mine.

[0027] The analysis device 30 is an information processing device such as a personal computer, and is equipped with an input unit 31 such as a keyboard, a display unit 32 such as a liquid crystal display, an output unit 33 such as a speaker, a storage unit 34 such as a flash memory, and a control unit 40.

[0028] The control unit 40 is an information processing unit such as a microcomputer equipped with a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. A control program for the analysis device 30 to execute a job is stored in the ROM. The control unit 40 reads out the control program stored in the ROM and expands the control program in the RAM, thereby controlling the analysis device 30 and functions as a measurement device registration acceptance unit 41, a measurement distance estimation unit 42, a strain monitoring unit 43, an unknown quantity estimation unit 44, and a compatibility determination unit 45.

[0029] The measuring device registration reception unit 41 receives the equipment ID of the strain measuring device 10 attached to the erected steel support 1, and stores the received equipment ID as measuring device information 341 that corresponds to the support ID of the steel support 1 and the installation position (ceiling surface, right side, left side).

[0030] When measurement data is input, the measurement distance estimation unit 42 refers to the measuring device information 341 based on the equipment ID to identify the installation position (ceiling surface, right side, left side) of the strain measuring device 10 that transmitted the measurement data, and estimates the measurement distance d to the face at the time of measurement based on the identified installation position (ceiling surface, right side, left side) and radio wave intensity.

[0031] When the measurement data is input, the strain monitoring unit 43 compares it with past measurement data at the installation position identified by the measurement distance estimation unit 42, and if the amount of change in the strain measurement value exceeds a preset danger threshold, a warning is issued from the display unit 32 and the output unit 33 to urge the worker to evacuate. This makes it possible to monitor strain in real time and issue a warning when strain increases.

[0032] The unknown quantity estimation unit 44 calculates the natural mass elastic modulus E by an inverse analysis method using the strain measurement value and the measurement distance d as measurement quantities. R and initial stress σ x0 , σ y0 , τ xy0 The back analysis method uses the two-dimensional elastic finite element method. First, the analysis model shown in Figure 3 is used to estimate the initial stress per unit σ x0 , σ y0 , τ xy0 and the elastic modulus of the rock mass E R is provisionally set and the strain (hereinafter referred to as unit strain) is calculated in advance.

[0033] Next, the unknown initial stress σ is calculated by calculating how many times the measured strain is the previously calculated unit strain. x0 , σ y0 , τ xy0 and the elastic modulus of the rock mass E RIn the analysis model shown in Fig. 3, the natural ground is an isotropic elastic body, and the initial stress σ x0 , σ y0 , τ xy0 is assumed to be constant throughout the entire analysis domain. Actual rock mass behaves inelastically and nonlinearly, but the analysis results are output as equivalent values ​​including these.

[0034] The suitability determination unit 45 calculates internal displacement and shear stress distribution by forward analysis using the natural ground properties estimated by the unknown quantity estimation unit 44, and verifies the suitability of the support by comparing it with the control values.

[0035] Next, a method for estimating the measured distance d by the measured distance estimating unit 42 will be described in detail with reference to FIG. In the measurement distance estimation unit 42, the distance A between the wireless unit 21 (antenna) and the tunnel face (for example, 8 m when the wireless unit 21 is placed at the center of the tunnel cross section) and the distances C1, C2, and C3 between the wireless unit 21 (antenna) and the ceiling surface, right side surface, and left side surface, respectively (for example, the tunnel diameter D / 2) are set as fixed values.

[0036] The measurement distance estimation unit 42 refers to the measuring device information 341 based on the device ID to identify the installation position (ceiling surface, right side surface, left side surface) of the strain measuring device 10 that transmitted the measurement data.

[0037] The measured distance estimation unit 42 also estimates the linear distance r (linear distance r1 when the attachment position is on the ceiling surface, linear distance r2 when the attachment position is on the right side surface, and linear distance r3 when the attachment position is on the left side surface) from the transmission source strain measuring device 10 based on the reception intensity. That is, the measured distance estimation unit 42 estimates the linear distance r using the property of a wireless signal that attenuates in proportion to the square of the distance.

[0038] Then, the measurement distance estimation unit 42 estimates the measurement distance d to the face at the time of measurement using any one of the distances C1, C2, and C3 corresponding to the identified installation position, the linear distance r, and the distance A. For example, when the installation position of the strain measurement device 10 is the ceiling surface, d=√(r1 2 -C1 2 ) + A is calculated to estimate the measured distance d to the face at the time of measurement.

[0039] Although the distance A between the wireless unit 21 (antenna) and the face and the distances C1, C2, and C3 between the wireless unit 21 (antenna) and the ceiling surface, right side surface, and left side surface, respectively, are set to fixed values, these may also be measured values ​​measured using a measuring device such as a laser rangefinder.

[0040] The estimated measurement distance d is the distance between the steel support 1 to which the strain measuring device 10 is attached and the face, and if the strain measuring device 10 is attached to the same steel support 1, the value should be the same. a Strain measurement device 10 installed on a1 , 10 a2 , 10 a3 The accuracy can be improved by adjusting the measured distances d1 so that they are the same value (for example, by averaging them).

[0041] Furthermore, if the distance L between adjacent steel supports 1 is known, a Strain measurement device 10 installed on a1 , 10 a2 , 10 a3 Measurement distance d a and steel support 1 b Strain measurement device 10 installed on b1 , 10 b2 , 10 b3 Measurement distance d b The accuracy can be improved by adjusting (for example, averaging) the difference between

[0042] Next, the unknown quantity estimation method performed by the unknown quantity estimation unit 44 will be described in detail with reference to FIG. First, the unknown quantity estimating unit 44 estimates the Poisson's ratio V R , Poisson's ratio of steel support 1 V L , vertical stress σ y0, the elastic modulus E of steel support 1 L The setting of the elastic modulus of the support E is accepted (step S101). L The input values ​​are the permeable elastic modulus of the steel support 1 (H steel) and the shotcrete. Poisson's ratio of the ground V R Although, is actually an unknown quantity, a general value (e.g., 0.35) is input to simplify the analysis.

[0043] The unknown quantity estimating unit 44 estimates the unknown natural ground elasticity coefficient E R The input of the natural soil elastic modulus E R is used as the initial value for the iterations.

[0044] The unknown quantity estimation unit 44 calculates the ratio R of the elastic modulus of the ground to that of the support structure. i =E L / E R Calculate (step S103).

[0045] The unknown quantity estimator 44 also receives the strain measurement value ε m ', when the measured distance d to the face at the time of measurement is received (step S104), the converged strain ε m is predicted from the strain characteristic curve (step S105).

[0046] Strain measurement value ε m ' is the value starting from the time when the steel support 1 was installed. The strain value after convergence ε m is a value starting from the start of excavation. The strain characteristic curve shows the measured distance d to the face and the ratio of the current strain to the converged strain, and is determined from an empirical curve if there is no excavation data. If it is assumed that the stress-strain relationship is linear, the strain characteristic curve can be determined from the internal displacement and the amount of crown settlement.

[0047] In addition, the ground begins to deform before excavation begins. The strain characteristic curve for the area where the distance to the face is negative can also be determined from the preliminary displacement measurement using a preliminary settlement meter, the amount of ground surface settlement, and three-dimensional analysis. Finally, the internal displacement and shear stress distribution are calculated using the determined ground properties, and the suitability of the support is confirmed based on the control values.

[0048] Next, the unknown quantity estimation unit 44 uses the following equations (6) and (7) by a back analysis method to calculate the natural ground elasticity coefficient E R and initial stress σ x0 , σ y0 , τ xy0 Calculate the ratio of the inverse analysis elastic modulus and update it (R i+1 =E L / E R ) (step S106).

[0049] In order to analyze the deformation caused by tunnel excavation using the finite element method, it is necessary to calculate the excavation external force Ρ acting on the inside of the steel support 1 using equation (1). The integral is the volume integral of the ground element. Since the initial stresses are all unknowns, each component σ of the initial stress σ0 x0 , σ y0 , τ xy0 External force component Ρ in units of i (i=1 to 3) is calculated using equation (2).

[0050]

number

[0051] In addition, the elastic modulus of the ground E R and the elastic modulus of the support E L The stiffness matrix when both are 1 is K R , K L Then, the overall stiffness matrix K is expressed by equation (3). The elastic modulus ratio of the ground and the support is the parameter R = E L / E R Then, equation (3) becomes equation (4).

[0052]

number

[0053] The finite element method finds the displacement u and strain ε by solving the stiffness equation Ρ=k u. Similarly, K * and the external force component P i When the strain of steel support 1 is measured at three points, the relationship between the unit strain at each measurement point is expressed by equation (5).

[0054]

number

[0055] The unknown matrix C is calculated by the least squares method using equation (6). y0 Assuming that is equal to the overburden pressure, it is given by equation (7) from the overburden h and the average unit weight of the ground γ. Then, the remaining ground elastic modulus E R and initial stress σ x0 , τ xy0 By repeating the above process, the unknown elastic modulus of the rock mass E R and initial stress σ x0 , σ y0 , τ xy0 and converge.

[0056]

number

[0057] Next, the unknown quantity estimation unit 44 calculates (R i+1 -R i ) / R i It is determined whether or not the error is less than a preset allowable error (step S107).

[0058] In step S107 (R i+1 -R i ) / R i If it is equal to or larger than the allowable error, the process returns to step S103 and the natural rock mass elastic modulus E calculated in step S107 is R The ratio of elastic modulus of the ground and the support, R i=E L / E R Recalculate.

[0059] In step S107 (R i+1 -R i ) / R i is less than the allowable error, the conformity determination unit 45 determines the natural ground elasticity coefficient E R and initial stress σ x0 , σ y0 , τ xy0 The inner displacement and shear stress distribution, etc. are calculated by a direct analysis using (step S108).

[0060] Then, the suitability determination unit 45 confirms the suitability of the support based on whether the calculated internal displacement and shear stress distribution are within the control values ​​or exceed the control values ​​(step S109).

[0061] If the internal displacement and shear stress distribution calculated in step S109 are within the control values, it is confirmed that the supports are suitable, and the process ends.

[0062] If the internal displacement or shear stress distribution calculated in step S109 exceeds the control value, it is determined that the support is non-compliant, and the compatibility determination unit 45 issues a warning to the worker via the display unit 32 or the output unit 33 to encourage the worker to review the support. This allows the worker to detect in advance the risk of a displacement exceeding the allowable value occurring in the future, and allows the worker to consider installing additional rock bolts or upgrading the steel support 1.

[0063] In this way, the measured strain value ε m Since ' is used as the input value, the deformation behavior of the ground can be captured at a relatively early stage and reflected in the back analysis. Also, since there are no limitations to the analysis model if it is elastic, it is easy to devise measures such as increasing the number of known physical properties. Furthermore, accuracy can be improved by correcting the strain characteristic curve based on excavation results.

[0064] As described above, the present embodiment is a strain measurement system for measuring the strain of a steel support 1 installed in a tunnel, and the strain measurement value ε m The system is equipped with a strain measuring device 10 that wirelessly transmits measurement data including ', and a monitoring device 20 that is installed on a drill jumbo 2, a tunnel construction work vehicle that works in front of the tunnel face, and monitors the strain of the steel support 1 using the measurement data received from the strain measuring device 10. With this configuration, no cable wiring or protective work is required to install the strain measuring device 10, so excavation does not need to be stopped to install the strain measuring device 10, and strain measurement and monitoring can be started near the face immediately after the steel support 1 is erected. The measurement data is then collected in real time by the monitoring device 20 installed in the drill jumbo 2. Since the system can be configured with only the strain measuring device 10 as a transmitter and the monitoring device 20 as a receiver, ground behavior can be predicted in real time without adding a new network inside the tunnel.

[0065] Furthermore, in this embodiment, when the monitoring device 20 receives the measurement data, it compares it with the past measurement data and calculates the strain measurement value ε m The device is provided with a strain monitoring unit 43 that issues a warning when the amount of change in strain ' exceeds a preset danger threshold. With this configuration, if an increase in strain occurs, an emergency evacuation order can be quickly issued to face workers.

[0066] Further, in this embodiment, the monitoring device 20 includes a measurement distance estimating unit 42 that estimates a measurement distance d to the face at the time of measurement based on the radio wave intensity at the time of receiving the measurement data, and a strain measurement value ε m The elastic modulus of the rock mass E R and initial stress σ x0 , σ y0 , τ xy0 The system is equipped with an unknown quantity estimation unit 44 that estimates the above as ground characteristics, and a suitability determination unit 45 that calculates internal displacement and shear stress distribution by forward analysis using the estimated ground characteristics and compares them with control values ​​to confirm the suitability of the support structure. This configuration makes it possible to capture the deformation behavior of the ground at a relatively early stage and reflect it in the back analysis.

[0067] Furthermore, in this embodiment, the measurement distance estimation unit 42 calculates the measurement distance d based on the straight-line distance r between the strain measuring device and the monitoring device 20 estimated based on the radio wave intensity at the time of receiving the measurement data, the straight-line distance C between the tunnel face (mounting position) on which the steel support 1 to which the strain measuring device 10 is attached is installed and the monitoring device 20, and the distance A between the face and the monitoring device 20.

[0068] The present invention has been described above based on the embodiment. This embodiment is merely an example, and it will be understood by those skilled in the art that various modifications are possible in terms of the combination of the respective components, and that such modifications are also within the scope of the present invention. [Explanation of symbols]

[0069] 1 Steel shoring 2. Jumbo Drill 10 Strain measurement device 11 Strain gauge 12 Bridge 13 Amplifier 14 Strain measurement section 15 Measurement result storage section 16 Communication Control Unit 17 Wireless Unit 18 Battery 20 Monitoring equipment 21 Wireless unit 22 Communication Control Unit 30 Analyzer 31 Input section 32 Display section 33 Output section 34 Storage section 40 Control section 41 Measurement Equipment Registration Reception Department 42 Measurement distance estimation unit 43 Strain monitoring section 44 Unknown quantity estimation part 45 Conformity determination section 341 Measuring Equipment Information

Claims

1. A strain measurement system for measuring strain in a steel support structure installed in a tunnel, A strain measuring device that is attached to the steel support and wirelessly transmits measurement data including a measured strain measurement value; A monitoring device is installed on a tunnel construction vehicle working in front of the tunnel face and monitors the strain of the steel support structure using the measurement data received from the strain measuring device. The monitoring device includes a measurement distance estimation unit that estimates a measurement distance to a face at the time of measurement based on radio wave intensity at the time of receiving the measurement data; an unknown quantity estimation unit that estimates a natural ground elastic modulus and an initial stress as natural ground characteristics by an inverse analysis method using the strain measurement value and the measured distance as measurement quantities; A strain measurement system characterized by comprising a suitability determination unit that calculates internal displacement and shear stress distribution by direct analysis using the ground characteristics and compares them with control values ​​to confirm the suitability of the support structure.

2. The strain measurement system according to claim 1, characterized in that the monitoring device is provided with a strain monitoring unit that, when receiving the measurement data, compares it with past measurement data and issues an alarm if the change in the strain measurement value exceeds a predetermined danger threshold.

3. The strain measurement system described in claim 1, characterized in that the measurement distance estimation unit calculates the measurement distance based on the straight-line distance between the strain measuring device and the monitoring device estimated based on the radio wave intensity at the time the measurement data is received, the straight-line distance between the tunnel face on which the steel support to which the strain measuring device is attached is installed and the monitoring device, and the distance between the face and the monitoring device.

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